Hornfels is a metamorphic rock formed by the contact between mudstone or other clay rich rock, and a hot igneous body, and represents a heat altered equivalent of the original rock
Coquina is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of molluscs, trilobites, brachiopods, or other invertebrates
From German which means hornstone
From Concha (Latin)+ Coquina(Spanish) +conch(English)= Couquina (mid 19th century)
Fine Grained Rock, Opaque Rock
Coarse Grained Rock, Opaque Rock